.list{
    width: 200px;
    border: 1px solid blue;
    overflow-y: auto;
    margin-top: 100px;
}

.item{
    border-bottom: 1px solid red;
    height: 40px;
}

.item:hover{
    background-color: lightskyblue;
}

.show-panel{
    display: none;
    width: 200px;
    height: 250px;
    text-align: center;
    line-height: 250px;
    border: 1px solid #cccccc;
    background-color: azure;
    position: fixed;
    left: 0;
    top: 0;
}